<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <style>
      #star-five {
        margin: 100px auto;
        position: relative;
        color: red;
        width: 0px;
        height: 0px;
        border: 100px solid transparent;
        border-bottom: 70px solid red;
        transform: rotate(35deg);
      }

      #star-five:after {
        position: absolute;
        display: block;
        top: -63px;
        left: -153px;
        width: 0px;
        height: 0px;
        border: 100px solid transparent;
        border-bottom: 70px solid red;
        transform: rotate(-70deg);
        content: "";
      }
      #star-five:before {
        border-bottom: 80px solid red;
        border-left: 30px solid transparent;
        border-right: 30px solid transparent;
        position: absolute;
        height: 0;
        width: 0;
        top: -51px;
        left: -65px;
        content: "";
        transform: rotate(-35deg);
      }
      #eg {
        margin: 100px auto;
        position: relative;
        color: red;
        width: 0px;
        height: 0px;
        border: 100px solid transparent;
        border-bottom: 70px solid red;
        transform: rotate(35deg);
      }

      #eg:after {
        position: absolute;
        display: block;
        top: -63px;
        left: -153px;
        width: 0px;
        height: 0px;
        border: 100px solid transparent;
        border-bottom: 70px solid yellow;
        transform: rotate(-70deg);
        content: "";
      }
      #eg:before {
        border-bottom: 80px solid blue;
        border-left: 30px solid transparent;
        border-right: 30px solid transparent;
        position: absolute;
        height: 0;
        width: 0;
        top: -51px;
        left: -65px;
        content: "";
        transform: rotate(-35deg);
      }
    </style>
  </head>
  <body>
    <div id="star-five"></div>
    <p>eg:五角星可分为两个大三角形和一个小三角形的组合 利用定位+旋转</p>
    <div id="eg"></div>
  </body>
</html>
